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How good is my corona defense – and why is that not so important. For BZ, Berliners had their antibodies counted. Laboratory doctor Dr. Michael Müller explains how it works.
Am I still protected against Corona? If I get infected now, will my body be able to cope with the viruses?
Many Berliners are currently concerned with this question. For some, the corona vaccination was more than six months ago, now they want to know whether the vaccination is still effective or whether a third, “booster” vaccination makes sense. Parents wonder whether their children may have been sick without even realizing it. Some are just curious whether their vaccination was successful.
Antibody tests promise an answer to these questions. They cost just 20 euros and are intended to show how many immune cells are in the body.
In Austria, the antibody tests are already considered evidence of a survived infection; in Switzerland, this is also being debated. In Germany, Health Minister Jens Spahn (41) asked for it. For certain groups, the tests are already approved as evidence of a disease.
BZ explains how the tests work, how meaningful they are, what they cost and what experts advise.
What is an Antibody Test?
It uses a complicated procedure to measure the so-called titre of proteins, the antibodies. This is the concentration of antibodies that were formed by the immune cells in the blood against the coronavirus.
How do the antibody tests work? What does it prove?
Dr. Michael Müller, Head of Laboratory 28 at Heidelberger Platz: “When the immune system deals with a virus such as SARS-CoV-2 for the first time, there is a complex interplay between the white blood cells of the immune system. They recognize the pathogen that multiplies in the human organism and fight it through various mechanisms. The immune system builds up a memory so that if you come into contact with the pathogen again, the defense can take place faster and more efficiently. This also includes the formation of antibodies by a subgroup of white blood cells called B lymphocytes.
These antibodies are able to bind and neutralize the pathogen at an early stage when humans come into contact again. With suitable test methods in the laboratory, we can recognize the different types of antibodies formed and, to a certain extent, estimate the amount formed. “
In which unit are antibodies measured?
Most tests measure Binding Antibody Units (BAU) per milliliter of blood.
When is a test positive?
This varies from manufacturer to manufacturer depending on the test. We use an IgG antibody test that is negative for values below 33.8 BAU / ml, positive above that. After infection and vaccination, the values vary greatly from person to person. However, some people also have 2000 BAU / ml.
Can a test tell me if my body is protected against the virus?
No. There are no limits to the level at which antibodies protect against infection. In general, the following applies: If antibodies are present, this usually speaks in favor of protection; whether many antibodies protect particularly well has not yet been proven.
Many experts and the Robert Koch Institute see it as critical to commit to numbers. And even with high antibody levels there is a residual uncertainty that you can still get COVID-19. Should everyone get an antibody test?
Dr. Michael Müller: “No, for most people the SARS-CoV-2 antibody determination is not useful or necessary for medical reasons.”
Who are the tests for?
Especially for people who have an immune disorder or who are on drugs that weaken the immune system. This can be chemotherapy, for example. Dr. Michael Müller: “Then the examination can be useful to see whether and to what extent the immune system, which is generally restricted, has reacted to the vaccination.”
When does the test make sense?
Dr. Michael Müller: “For vaccinated people only when the immune cells have formed, i.e. two to three weeks after the vaccination at the earliest, the STIKO (Standing Vaccination Commission) recommends at least four weeks between the vaccination and the antibody test. If you want to find out whether you have gone through an infection, the test can also only become positive after a few weeks. “
Can you find out whether you need a booster vaccination?
No. So far, the test has only shown when a vaccination has hardly had any success, especially in people with an immune disease.
Why is there no clear result?
Dr. Michael Müller: “The fluctuations are very large from person to person. This also depends on the amount of viruses ingested and the duration and severity of the course of the disease in the case of a SARS-CoV-2 infection. It happens that we can only temporarily detect a small amount of antibodies in the blood of people who have had a mild SARS-CoV-2 infection. In other cases it is different, and we detect longer and more antibodies. “
Then what are the tests good for?
Dr. Michael Müller: “In short, it can be said: If specific SARS-CoV-2 antibodies can be detected, this speaks for a natural infection or a vaccination. However, the other way around applies: If the test is negative, a previous infection or a vaccination cannot be excluded. And even if the detection of antibodies in the bloodstream is not successful, the immune system is usually able to react specifically and effectively to SARS-CoV-2 via its “immunological memory”. “
Can a corona infection be detected using antibodies?
Dr. Michael Müller: “No, antibody tests are not suitable for reliably detecting an infection in people with symptoms. The SARS-CoV2-PCR test remains the method of choice for diagnosing the infection. “
What do the tests cost?
Similar to a corona rapid test around 20 euros. However, they are determined in ultra-modern laboratories and apparatus. You get the result after a day. The tests can also be bought at home on the Internet, but experts advise against them.
Do mass tests for antibodies make sense?
Dr. Michael Müller: “Yes. There are already a number of population studies, including in Berlin, where a large number of people have been examined for the presence of SARS-CoV-2 antibodies. They are primarily used to make statistical statements about the spread of COVID-19 and thus to make infection-epidemiological assessments of the pandemic. “
Can I also take the test at home?
Dr. Michael Müller: “In my opinion, rapid antibody tests“ at home ”are not well suited. They are not subject to such strict quality assurance requirements as the tests that have been carried out by a medical laboratory trained for this purpose after blood has been taken by the general practitioner or specialist. “
If I have antibodies, can I no longer pass the virus on?
Dr. Michael Müller: “Yes, because even as a vaccinated person I can pick up viruses again, that is, I can become infected and then pass on viruses, even if such an infection is usually mild in people who have been vaccinated. This is why the “AHA plus L rule” should always and especially with the now higher infection numbers, where the likelihood of encountering infected people who may not yet know, be observed, i.e. wear distance, hygiene, mask and indoor ventilation. “
Should an antibody test be used as a convalescent card?
Dr. Michael Müller: “Basically yes, if it was carried out by a quality-assured laboratory.”
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